Stents, grafts, covered stents, vascular endoprostheses, struts or other endovascular devices of various shapes, sizes, and materials are generally used as therapy for minimally invasive treatment of various conditions such as, for example, vascular aneurysms (especially in the aorta) atherosclerotic plaque at risk for rupture, vascular occlusion, stenosis, or other indications. These endovascular devices may be made of various materials such as, for example, PolyTetraFluoroEthylene (PTFE or Teflon) with Nickel-Titanium (nitinol), stainless steel, and/or other material.
Placement of such endovascular devices is generally performed with x-ray guidance, often a portable C-arm fluoroscopy system that can be wheeled into an operating room for monitoring the location of the device before and during deployment. Exact positioning is crucial to successful outcomes. Placement errors as small as one millimeter may result in stroke, thrombus (clot), or “endoleak” (i.e., where blood leaks around the outside of the graft and into the aneurysm), making the therapy ineffective and potentially dangerous.
For example, knowledge of the exact location of vessels that branch off the aorta (such as carotid artery, renal arteries, celiac artery) may be critical to the success of placement of an endovascular device. As such, treatment planning often involves detailed measurements of aortic diameter at multiple locations, as well as an assessment of exact length of a graft or device required. Consideration as to location of calcium and atherosclerotic plaque is also given, so that severely diseased segments of the aorta may be avoided as potential landing spots. Furthermore, there is relatively little information currently available on where the spinal and lumbar arteries arise in relation to an aneurysm, and there is a relatively high incidence of damage to the spinal cord, which may result in paralysis and paresis as direct complications of a placement procedure.
Therefore, the ability to directly use pre-operative imaging such as, for example, Computed Tomography Angiography (CTA), Magnetic Resonance Angiography (MRA), and x-ray angiography, or other imaging during stent or stent/graft placement may improve the accuracy of the placement procedure by giving real-time feedback of location of branch vessels and enabling minor adjustments to avoid covering or landing a strut or fold of an endovascular device in critical vessels, calcium, or plaques. Other advantages may also be realized with the direct use of pre-operative imaging during placement procedures.
Current techniques involve confirming device location after placement of the device in its non-deployed state. This is generally done with angiography and conventional vessel road mapping, or plain fluoroscopy with reference to bones. However, there is little to no ability to correct for breathing or cardiac cycle motion during the deployment. It is therefore difficult both to plan the ideal deployment location and to carry out accurate placement according to the plan.
Current standard training videos and training modules show no roadmapping at all, or roadmapping without dynamic referencing. Some widely used training materials show an “expert” surgeon drawing on a monitor with a marker pen to show where the surgeon wants to place the endovascular device in relation to an x-ray fluoroscopic image that does not have vessels opacified.
Furthermore, referencing during endovascular device procedures is often performed by comparing bony landmarks on 2-dimensional x-ray images. However, this does not accurately reflect the exact location of target structures or non-target structures at any given point in time, which increases the inaccuracy of placement procedures.
These and other problems exist in current techniques.